The invention relates to a medical instrument with a shaft which has a distal end and a proximal end, with a jaw head, which is arranged on the distal end and has two jaw parts, of which at least one is pivotable.
An instrument of this kind in the form of a medical forceps is known from U.S. Pat. No. 5,827,323. Both jaw parts are movable and are mounted pivotably about a common axis at the distal end of the shaft. Each of the jaw parts has a toothed wheel portion arranged concentrically around the pivot axis. This toothed wheel portion meshes with a toothed distal end of a rectilinearly extending stiff actuation element. Thus, an elongate rod-shaped actuation element is present in the shaft for each jaw part, said actuation element being provided with a corresponding toothing on the side facing towards the toothed wheel portion of the jaw part. Thus, when one of the actuation elements is moved axially to and fro in the shaft, this movement is converted via the toothed engagement into a pivoting movement of a jaw part.
The toothing or meshing is configured such that the toothed wheel portion of a jaw part, when the latter is oriented approximately linearly with the shaft, is in engagement with the outermost distal end of the toothed wheel portion. If this actuation element is now moved in the distal direction, the jaw part pivots out from the linear orientation with the shaft, or with the central longitudinal axis of the latter, and is thus opened.
A disadvantage is that the distally advancing linear end portion extends more and more distally beyond the toothed wheel portion the further the jaw part is pivoted. These distally advanced end portions therefore occupy a considerable space distally in front of the articulation area of the pivotable jaw parts. In the final analysis, a pointed structure results, which is formed by the two distal end portions of the actuation elements provided with the toothing.
If such forceps are to be inserted into body cavities that are narrow or difficult to access, this “point” formed by the distally protruding distal end portions gets in the way. A possible area of use lies in the area of the frontal sinuses. There, a forceps-like instrument of this kind is pushed into the nasal opening initially with a rectilinear orientation of the jaw parts, after which the latter are introduced into the paranasal sinus or frontal sinus through an aperture, a so-called window. The space available there is small, especially in children for example, such that there is already little room for manoeuvre of the pivotable jaw parts. If the person operating this instrument wishes to work with the jaw parts pivoted out far to the sides, a relatively long “point” juts out in the direction of the longitudinal axis of the shaft, which “point” is formed by the advanced distal end portions of the actuation elements.
This makes the manipulation awkward.
US 2003/0100892 A1 discloses to pivot the jaw head and the jaw parts via cable pulls. However, very complicated structures are needed, namely a large number of cables and pulleys for controlling the different pivoting movements. Since considerable forces have to be applied to the jaw parts when separating tissue, for example cartilage, it is necessary to guide the cables with a high degree of tensioning around the pulleys of the cable pulls to ensure that they do not slip. If, as has already been mentioned, devices of this kind are intended to be used where there is little space available, they have to be made correspondingly slim, and therefore elaborate cable pull mechanisms of this kind are bulky and cannot have the required stability. In addition, complicated movement mechanisms of this kind are difficult to clean.
It is therefore an object of the present invention to further develop a medical instrument of the type mentioned at the outset in such a way that, with a control system that is as simple as possible and takes up little space, it is possible to achieve a high degree of flexibility and numerous degrees of freedom of movement of jaw head and jaw parts.